Electric machines, e.g., electric motors and generators, are used in a variety of industries to convert electrical energy to mechanical energy, and vice versa, for useful purposes. For example electric machines are used in the automotive, aviation, maritime, and other industries to operate aircrafts, helicopters, automobiles, boats, submarines, trains, and/or any other suitable vehicles.
To reduce fuel consumption and improve propulsive efficiency, it is generally desirable to use electric machines with large power densities, referred to herein as the electric machine's specific power or power-to-weight ratio. Electric machines having a high specific power may be smaller and more lightweight while generating equivalent or greater power than heavier electric machines.
Increasing rotational speeds of electric machines is known to increase power-to-weight ratios. However, as rotational speeds increase, the stresses on the various rotating components of the electric machine also increase. As a result the retaining structure for holding the rotating components of the electric machine must be larger and heavier, thus increasing costs, size, and weight. For example, certain electric machines use a disk retaining structure which allows for much higher tip speeds and power densities than conventional machines. However, as the rotor disk experiences large centrifugal forces during high speed operation, the stresses exerted on rotor disk by the rotor components may limit the ability of the electric machine to reach higher speeds.
Accordingly, an electric machine with features for improving specific power and efficiency is desirable. More specifically, an electric machine with features for enabling high speed operation of the electric machine to improve performance and specific power would be particularly beneficial.